Conventionally, various types of substantially plate-shaped piezoelectric speakers in which a piezoelectric polymer sheet is used have been proposed. The piezoelectric speakers with a piezoelectric polymer sheet have, for example, a piezoelectric polymer sheet and opposing electrodes formed on both sides of the piezoelectric polymer sheet, such as a flexible speaker disclosed in Patent Document 1. In response that a voltage is applied between the opposing electrodes, an electric field works on the piezoelectric polymer sheet, and the piezoelectric polymer sheet distorts. This distortion is utilized to generate a sound.    Patent Document 1: Japanese Laid-open Patent Publication No. 2009-272978